Play as a Jet Trooper. Go to the very high bridge where you can snipe. Go to the end. Fly to the waterfall. There will be a thin area in between the invisible walls where you can get through. Once you are on top of the waterfall, you will encounter sudden invisible walls and places with invisible pillars. You can go to the very end where there is a continuous invisible wall and become stuck. After about ten minutes, the invisible walls surrounding you will disappear.